The portable version is a work in progress. There are no releases yet.
The official Game of Trees -portable Git repository can be cloned from git.gameoftrees.org:
git clone https://git.gameoftrees.org/got-portable.git
Git protocol access is also available if needed, but is discouraged because it does not use encryption:
git clone git://git.gameoftrees.org/got-portable.git
A web interface for browsing is also available: https://git.gameoftrees.org/gitweb
The linux branch in the got-portable repository provides support for Linux-based systems. The file README.portable contains installation instructions.